Lightning can cause considerable damage to aircraft in flight, for example civil transport airplanes. In order to protect these aircraft and to minimize the damage that can be caused by lightning, it is known to place lightning conductor protection strips on the radome of aircraft, situated in the nose cone of the fuselage. Generally speaking, said radome makes it possible to protect a radar and, as a result, is typically made of a material permeable to electromagnetic waves, for example an electrically insulating composite material, usually more flexible and more deformable than the structure of the fuselage on which said radome is fixed.
A first type of known lightning conductor protection system consists in placing lightning conductor protection strips, in particular in the form of metal strips, on the external face (or external skin) of the radome. In order to minimize problems of aerodynamics linked to the presence of metal strips on the surface of the radome, these are laid out in a radial manner, starting from the periphery of the radome and aiming towards the tip thereof The metal strips are moreover electrically connected to the ground of the aircraft. Thus, when lightning strikes the radome, the metal strips guide the lightning to the ground of the aircraft.
In order to eliminate any problem of aerodynamics, a second type of lightning conductor protection system in which the metal strips are positioned inside the radome (on the internal skin of the radome) has also been envisaged in the prior art. French patent application FR 2 924 686 A1 describes an example of such a lightning conductor system for aircraft comprising metal strips fixed to the internal face of the radome. The lightning attachment on the radome then operates by means of metal studs flush with the external face of the radome. The metal strips are also laid out in a radial manner on the internal face of the radome.
FIG. 1A represents, in section, an example of such a lightning conductor system 10 of the second type according to the prior art. A metal fixing stud 3, in particular a fixing screw, of principal axis X, connects the external face 1a of the radome 1 to an internal metal lightning conductor strip 2, in particular trapezoidal, provided with a through orifice 8 (visible in FIG. 3A) for the fixing stud 3 and situated on the internal face 1b of the radome 1. The fixing stud 3 is fixed in the wall of the radome 1 via an insert 6 (or cross strut) and a fixing resin 5. The lightning conductor strip 2 is screwed to the fixing stud 3 by means of a fixing nut 4. Lightning F that strikes the fixing stud 3 on the side of the external face 1a of the radome 1 is guided to the lightning conductor strip 2 situated on the side of the internal face 1b of the radome 1. FIGS. 2A and 3A show in perspective, respectively in an assembled configuration and in an exploded configuration, the lightning conductor system 10 of FIG. 1A, whereas FIG. 4A represents, in frontal view, an example of radome 1 comprising a plurality of lightning conductor systems 10 according to the prior art and FIG. 5A represents an enlarged view of part A of FIG. 4A.
Although this second type of lightning conductor system 10 makes it possible to resolve any aerodynamics problem, this solution is not entirely satisfactory, particularly for the reasons exposed hereafter. In fact, the conception of this lightning conductor system 10 of the prior art generally leads to a complexity in the machining and the assembly of the lightning conductor strips 2 and, as a result, an increase in costs. In particular, the main axes X of the fixing studs 3 are merged with the axes of piercing of the lightning conductor strips 2, so that the fixing studs 3 and the lightning conductor strips 2 are connected together and impose precise tolerances and a complicated assembly of the lightning conductor systems 10. In addition, as may be observed in FIG. 5A, the solution of the prior art may bring about difficulties of localisation during the fixing of the lightning conductor strips 2 on the radome 1. In fact, during assembly, it is necessary to be able to ensure that all of the orifices formed in the wall of the radome 1 for the passage of the fixing studs 3 are opposite orifices formed in the lightning conductor strips 2 and then, in the case of too great a difference, it is sometimes necessary to carry out complex and costly adjustments. Moreover, the lightning conductor strips 2 of this lightning conductor system 10 of the prior art may also exhibit a too important failure of radio-electric barrier vis-à-vis radar waves of the radome 1.